1. Field of the Invention
2. Description of the Related Art
The expert in the field knows how to use RDS-TMC (Radio Data System-Traffic Message Channel) to transmit traffic information pertaining to a highway network from a traffic information control center to a terminal, where traffic information pertaining to each segment of the highway network is transmitted, and the traffic data, thus transmitted segment by segment, can be decoded in the terminal by the use of a coding/decoding table available there into a form suitable for presenting the data to the terminal user. This widespread method, however, is a very complicated way of transmitting traffic data in view of the quantity of data to be transmitted, especially so for the transmission of traffic data which remain unchanged over several segments of the highway network.
The task of the present invention is to create a method and devices which make it possible to transmit traffic data efficiently in the simplest and cheapest possible manner.
The invention makes it possible to transmit traffic data pertaining to several segments of a highway network, where the amount of data to be transmitted is relatively small. The traffic data to be transmitted include in particular the conditions of one or more segments of the highway network such as the travel time in this segment, the average speed there, the number of vehicles, the size of the traffic congestion, the presence of construction sites, drivers driving in the wrong direction, and weather conditions.
Transmission according to the invention is suitable both for conditions which remain the same over several segments (and thus suitable for traffic data to be transmitted which remain the same) and for traffic data pertaining to physically adjoining segments in which the conditions differ.
For the transmission of traffic data pertaining to a condition which is continuous over several physically adjoining segments of a highway network, it is possible to transmit, for example, the first or the last of these segments, the number of segments, and the condition. To transmit traffic data pertaining to different conditions (average speeds, etc.) in several physically adjoining segments of a highway network, it is advisable to transmit the first or the last of these successive segments, the number of segments, and the condition of each segment or of at least one segment (advisably the condition applicable to just one segment in each case) in the physical sequence in which the segments are arranged. In both cases, it is advantageous that there is no longer any need to identify each segment with the exception of the first or last segment, which means that the quantity of data to be transmitted is significantly reduced.
A segment table (advisably identical to that in the traffic data control center) is available in the terminal. In the segment table, it is advisable for the segments following each other in sequence in the highway network to carry successive segment numbers. A set of output instructions for a digital map database (e.g., for optical display or acoustic output) can be stored in memory in association with the segment numbers of the segments; for example, a chain of segments (which represent one or more lanes in one or more travel directions of an autobahn in the real highway network) can represent a lane in a two-dimensional display of the highway network. A segment can represent a section of an autobahn, so that, when the traffic data, including the segment and its condition, are transmitted, a test sequence for this segment (such as xe2x80x9cAutobahn A57 between Dxc3xcsseldorf and Colognexe2x80x9d) and possibly also a text sequence for the condition (e.g., xe2x80x9ccongestionxe2x80x9d) can be found in the segment table stored in the terminal, and these texts can be generated acoustically.
The data are transmitted by radio, especially mobile radio broadcast (GMS-SMS-CB). News summary transmission is especially suitable. In digital mobile radio networks, broadcast transmission (cell broadcast) is possible.